Buying a diving equipment, as any other specialist equipment, should be carefully planned and considered. It is easy to buy any diving equipment and spend a lot of money on itbut in the end it may turn out that the equipment doesn’tsuit a diver. Before buying, a diver should rent some equipments and try them underwater. Only then one can decide what’s the most important for them in diving equipment, what’s the most comfortable and what gives the best control underwater.

Shopping should start even before taking a course with buying a mask, flippers (fins) and a snorkel.

Diving mask is a must for divers and snorkellers as it enables them to see clearly underwater. Mask has to fit the face. It cannot be too lose nor too tight in order to allow a diver to breathe out through the nose into the mask. That prevents squeezing on descent when the pressure increases. The faceplate of the mask is also important. It should be sturdy and made of tempered glass. Masks with plastic or low-quality glass plates are not recommended. Common types of masks are: mask with one or two windows and a cutout for the nose and a double-dome mask that gives a wider field of view than traditional mask. In order to avoid fogging up two methods can be used. One can use commercial products or the saliva and wipe it around the inside of the faceplate and then wash the mask.

Flippers

Flippers (also called swim fins or simply fins) provide better propulsion than feet, improve the kick strength, foot flexibility and thus allow divers to swim efficiently. Flippers are made of rubber, foam or plastic and they are available in thousands of shapes, colours and fastenings. Fins should be tried on a wet foot. There are many types of fins for different groups of users. For example, scuba divers need large wide fins in order to swim when burdened with heavy equipment and snorkellers use light elastic fins. The general diver’s fitness is also important. Very strong and fit divers can go for stiff fins. Divers who have a less efficient kick should choose softer and more flexible fins. It is easier to swim with flexible fins but the swim is slower. Of course, one can choose from stiff, semi-stiff, semi-flexible, etc. The difference lies also in blades which can be: paddle-shaped with single blade (often called jetfins), split blade (often called biofins), blade with a v-shaped cut similar to fish tail. There are also flippers for free-diving which are similar to the paddle-shaped monofins but longer. They improve the acceleration of the swim and can be made of plastic, fiberglass or carbon fiber. Flippers can be full-foot, perfect for warm-water diving, or with a strip. The latter are used with neoprene dive boots and thus are commonly used in cold-water diving.

Snorkel

Snorkel is usually a J-shaped tube made from rubber that allows a diver to breathe underwater when swimming on the surface (skin diving) with the mouth and nose submerged. Snorkels are thirty to maximum forty centimeters long. If they were longer, a snorkeller (and his lungs) would be able to submerge more but the higher water pressure would make it impossible to fill the lungs with air. There is no special training required to use the snorkel. One has to just learn how to breathe through the mouthpiece and tube.

Diving suit

Diving suits are waterproof costumes which protect divers from underwater environment, especially temperature, sharp objects and underwater life. It is a protection from cold and hypothermia as diving suits help to keep the body temperature close to normal. Suits also provide defence from sun exposure, irritation, burns and scrapes being a kind of isolation. Diving suits are usually made from neoprene. Suits add some buoyancy and weights or weight belts must be worn to neutralize this drawback. There are different types of suits: dry suits, wetsuits, semi-dry suits and dive skins.

Dry suits

Dry suits are designed for cold-water diving (between -2 and 15°C) and to prevent water entering thanks to the seals at the neck and wrists and waterproof zippers. In order to work properly and protect the diver suits work with neoprene foam or air-containing fabric providing air pockets between the body and the cold water. There are four main types of dry suits according to the material:

- Foam neoprene suits are similar to wetsuits and the warmest at shallow depths. However, in greater depths the neoprene compresses and both thermal protection and buoyancy are limited.

- Shell suits are made from nylon. They are very light but inextensible and they provide little protection from cold.

- Vulcanized rubber suits are the best for diving in contaminated water. Thy are easy to put on and repair.

- Crushed neoprene suits don’t compress at depth because they have already been compressed. Thus they don’t lose their properties (thermal protection and buoyancy). They are very durable and flexible.

Wetsuits

Wetsuits are mainly designed for warm-water diving (between 10 and 25°C). They are made from thin neoprene and they protect divers from sun. However, there are also thick wetsuits (up to 8 mm) for cold-water diving (to 8°C). Generally, wetsuits work on similar basis as dry suits. Unlike dry suits, wetsuits don’t prevent water entering but trap a small amount of water inside the suit (insulator). Thus a suit cannot be too tight (a diver won’t be able to move or breathe) nor to loose (a diver will carry litres of water and the suit won’t protect them). The description of wetsuits thickness, for example 4/3, means that torso thickness is 4 mm and limb thickness is 3 mm. Thicker suits provide better protection from cold but restrict movements. Depending on the usage, one can choose from one-piece suits or combo, shorty or lengthy:

Semi-dry suits are very much like wetsuits but with wrist and ankle seals added. They are usually made from thick neoprene. Their properties change at depths (less thermal protection, negative buoyancy).

Dive skins

Dive skins are thin, one-piece suits designed for warm-water diving (above 25°C). They rather don’t provide thermal protection but they protect from scrapes, abrasions and burns. Dive skins are made from elastane (spandex) or lycra.

Scuba weights

Besides all breathing devices and suit, one of the most important pieces of diving equipment is the scuba diving weights. They are essential because they are responsible for diver’s ascent and descent. Scuba diving weights are to maintain proper buoyancy and balance positive buoyancy underwater. There are numerous variants of colours and shapes of diving weights. But the most important factor one must pay attention to is their own body weight which determines the amount and the kind of weights. Usually, weights are inside a weight belt which is worn around diver’s waist. However, if these weights are insufficient, one need additional wrist and ankle weights.

Generally, there are two scuba diving weight systems. One is a nylon weight belt with separately selected weights (from 0,45 kg to 4,5 kg). The alternative is a buoyancy compensator with an integrated weights system. When using this system, one doesn’t need to wear a separate belt or additional wrist and ankle weights. There are different types of weights including: soft, vinyl coated, uncoated and ankle weights.

Regulators

Regulator is one of the most important pieces of diving equipment. It reduces the pressure of the breathing gas from the cylinder and delivers gas at ambient pressure to the mouth and thus allows breathing. There are different types of regulators. The simplest are constant-flow regulators.

Regulator consists of two parts: the first and the second stage linked through a diver’s hose. The first stage is the valve which reduces the breathing gas pressure from the cylinder. The valve lowers the flow of the breathing gas to about 9 bar from 138 bar. The first stage consists of pressure chambers which are separated with pistons (or diaphragms) that compress the airflow depending on the current pressure. Pistons open up at higher pressures and close at lower pressures. The second stage is responsible for inhaling and exhaling processes through the mouthpiece. It captures the pressure coming from the first stage through the hose. Then the air is delivered to the mouthpiece. The second stage may have different forms: direct feed, demand valve, octopus, etc. Direct feed is operated by the diver with a button, lever, or knob. Demand valve delivers the breathing gas when the diver starts inhaling.

Diving cylinders

Diving cylinders (also called scuba tanks or diving tanks) are used to store and transport the compressed breathing gas. It supplies the diver with the breathing gas through the diving regulator. A diving cylinder can hold a volume of between 3 and 18 litres. Maximum pressure is 200 to 300 bar. A 3-litre cylinder filled to 232 bar can contain almost 700 litres of compressed gas. A diver consumes normally 10-25 litres per minute. A professional diver can carry one or more tanks, depending on the needs. Generally, one tank is enough when warm-water diving and more tanks when cold-water diving or diving with low visibility.

The diving cylinder ismainly composed of the pressure vessel, the pillar valve, and Y pillar valve. The pressure vessels can be made of forged steel (4-5mm thick) or cold-extruded aluminium (11mm thick, with flat bottom). The pillar valve is the point where the pressure vessel is connected with the diving regulator. It is a seal and it controls the air flow. The Y pillar valve consists of two outputs and two valves. It allows two regulators to be connected to the cylinder. When one regulator fails (freeflows), the valve closes and the diver breathes from the regulator of the other valve.

Despite the underwater use, diving cylinders are also used to store gas for oxygen first aid treatment, emergencies, etc. Tanks should be filled only by professional suppliers (e.g. dive stops). It is required that cylinders are correctly labeled with their contents. The tanks are also coloured due to the content (e.g. air and nitrox – black and white quadrants on the cylinder’s shoulder, trimix – white, black and brown, oxygen – white, helium – brown). The cylinders must be regularly tested – the hydraulic test every 5 years, the visual test 2,5 years after a hydraulic test (in the EU). The mini cylinders (0.5 litre) must go through the hydraulic test every 4 years, and the visual test every 2 years.

Breathing gases

Nitrox

Nitrox is a breathing mixture similar to air and contains oxygen and nitrogen. However, nitrox usually contains more than 21% oxygen. It is used for dives to moderate depths during which there is no great risk of oxygen toxicity. Lower percentage of nitrogen reduces nitrogen narcosis and the risk of decompression sickness. It is also used for deep diving in order to accelerate decompression times. Mixture is selected to a particular dive according to depth and duration. Nitrox mixtures are marked EAN (enriched air nitrox) with a percentage of oxygen constituent. For example, EAN36 mixture contains 32% of oxygen. Using nitrox in recreational diving is controversial. The mixture has to be specially prepared. The use of nitrox requires also some special training.

Trimix

Trimix is a breathing mixture of three primary gases: oxygen, nitrogen and helium. It is used by technical divers. The role of helium is crucial in the mixture. It is used to reduce the proportions of oxygen and nitrogen and thus to diminish nitrogen narcosis and to allow longer and deeper diving without a risk of oxygen toxicity. Trimix mixtures are named by the oxygen and helium percentage. For example trimix 10/50 contains 10% of oxygen, 50% of helium and 40% of nitrogen.

Heliox

Heliox is a breathing mixture of helium and oxygen. Usually, it is used by professional divers, usually to depths greater than 60 meters. The main advantage of diving with heliox is that there is no risk of nitrogen narcosis. However, heliox has its drawbacks. Helium conducts heat faster than nitrogen and divers get colder than divers breathing other mixtures. The helium’s density is smaller than the density of air, so the divers’ voices may be high-pitched (like Donald Duck).

Rebreathers

A rebreather is a self-contained breathing set that supplies the diver with the breathing gas and partially or completely reuses the exhaled air (absorbs the carbon dioxide and adds the oxygen or gas mixture from the cylinder). It enables a more efficient use of gas. Another advantage of using rebreathers is their silent operation due to reduced volume of exhaled bubbles (semi-closed rebreathers) no bubbles at all (closed-circuit rebreathers).

Rebreathers typically consists of a breathing loop with a mouthpiece, tubes that transport the inhaled and the exhaled air, and a breathing bag. A breathing bag (often called a counterlung) serves to store the gas – it inflates when exhaling, and deflates when inhaling. However, a rebreather would not work without a CO2 absorbent canister. This piece removes carbon dioxide from the breathing gas. The set would not be complete without an oxygen source that injects the gas to the circulation. Proper functioning of a rebreather is possible thanks to the valves (an upstream check-valve and a downstream check-valve). There are three main types of rebreathers: oxygen rebreathers, semi-closed rebreathers, and closed-circuit rebreathers.

Oxygen rebreathers

An oxygen rebreather is the oldest and the simplest type. It consists of two stages: constant flow and a bypass. This type of rebreather supplies only pure oxygen either at a constant rate or at a rate that matches the metabolic consumption rate with a use of mechanical valve. The oxygen rebreathers are limited in function to a depth of about 6 meters due to the toxic properties of pure oxygen inhaled at pressure.

Semi-closed rebreathers

In a semi-closed rebreather the gas mixture (nitrox or trimix) is injected into the breathing loop at a constant rate. The excess gas that is not consumed by the diver (usually nitrogen or helium) is vented out of the breathing loop (very small bubbles). The gas mixture in the cylinder has to match the diving depth (maximum operating depth). Semi-closed rebreathers as well as closed-circuit rebreathers are not limited in function in terms of depth.

Closed-circuit rebreathers

Closed-circuit rebreathers also supply the gas mixture but in a different way than semi-closed type. All the gas is recycled (no bubbles emitted). A closed-circuit rebreather has two independent gas supply cylinders. One of them injects pure oxygen into the breathing loop. The other cylinder (called diluent) contains compressed air or gas mixture (nitrox, heliox, neox, or trimix). Thanks to electronic oxygen sensors, closed-circuit rebreathers maintain a comparatively constant partial pressure of oxygen in the breathing gas and automatically adds oxygen to the breathing loop when the partial pressure of oxygen drops below the set point.

Buoyancy compensators

Buoyancy compensators (BC, buoyancy control devices) are worn by the divers for two reasons: for life saving emergencies above and under the water and also to control and adjust the buoyancy trim. A buoyancy compensator can be back mounted, front mounted or jacket style. However, every buoyancy compensator consists of a mechanically or manually inflated bladder and a purge valve.

Back mounted buoyancy compensators

A back mounted buoyancy compensator (wings) consists of two inflatable bladders that are attached by a harness (together with the cylinders). It provides buoyancy at the back of the diver. The main advantage of the wings is the great lift they give and the proper and comfortable diver positioning underwater. They are also capable to expand to a large volume and thus be very buoyant. Wings are especially recommended for divers carrying two or four large cylinders, for divers of smaller build and for deep diving. The lift at the back allows a horizontal position underwater but can cause the face-down problem at the surface, especially if inappropriately worn.

Jacket style buoyancy compensators

A jacket style buoyancy compensator (also called a stabiliser jacket or a waistcoat) has a form of inflatable vest and is mounted like a jacket. The bladder of a stab jacket can extend either around the diver’s sides or at the diver’s back. The first type allows to maintain balance easily above and under the water. However, it may have a squeezing effect of the diver’s trunk. The stab jacket that extends only at the diver’s back does not cause any squeezing effect but can bring about a face-down problem at the surface. This type of buoyancy compensator is the most common.

Front mounted buoyancy compensators

A front mounted buoyancy compensator (also called a diver’s lifejacket or a horsecollar) is worn around the chest and the neck. Bladder in the front of the diver can however cause a face-up problem at the surface. This type is the cheapest but it does not provide so high buoyancy as the other compensators.

Diving gloves

Gloves may seem insignificant and divers often do not attach much importance to them. However, gloves are an essential part of the equipment. Depending on the type, gloves ensure protection from abrasion, thermal protection, and/or impermeability. Gloves, as well as a diving suit, should be well-fitted. Even in not very cool water, too loose gloves can make a diver shiver with cold. There are different types of gloves designed for diving in warm water (above 22°C), in cool water (15-22°C), in cold water (8-15°C) and in extreme cold water (below 8°C). Gloves also protect the diver’s hands (e.g. during wreck diving). They can be made of cotton, neoprene, or rubber (usually with an inner insulating layer of silk, cotton, or fleece). In order to add some protective properties, gloves can be coated with Kevlar, leather, or rubber. Dry gloves can be fitted with an O-ring seal or a zip.

Wetsuit boots and neoprene socks

Wetsuit boots (bootees or booties) have the similar purpose as the diving gloves. They help to keep warm feet during diving and also protect a diver from various sharp things on the sea bed, rocks and reefs. Similarly to diving gloves, the thickness of the boots should match the temperature of water. Soles of wetsuit boots are usually reinforced. The alternative for the wetsuit boots are the neoprene socks. They give little thermal protection but they are thin enough to be used with full-footed flippers.